Prismatic Configuration Research Articles

Muconato‐bridged Manganese Coordination Polymer exhibiting rare Distorted‐trigonal Prismatic Coordination Arrangement

Novel poly[Mn(H2O)(dmb)(muco)] (1) (H2muco = trans,trans‐muconic acid; dmb = 5,5′‐dimethyl‐2,2′‐bipyridine) was obtained by self‐assembly, one‐pot, solution reaction. 1 crystallizes in a monoclinic system with P21 space group and forms an infinite one‐dimensional (1D) polymer. Remarkably, the six‐coordinate MnII display a rare distorted trigonal prismatic configuration. This unusual coordination arrangement appears to be acquired due to the supramolecular interactions of the polymeric structure of 1, mainly throughout hydrogen bonding, giving rise to a 2D framework. Magnetic properties measurements reveal that 1 possesses weak antiferromagnetic interactions with θ(C–W) = –1.0 K and J = 458 cm–1.

Chloro‐Bridged Hexanuclear Pd(II) Clusters Supported by cis‐Blocking Tris(imido)phosphate Trianions

AbstractTransition metal complexes derived from anionic polyimido ligands are very limited in the literature. Here we describe the deprotonation of alkyl substituted phosphoric triamides with bis(benzonitrile)palladium dichloride which results in the formation of chloro‐bridged hexanuclear palladium(II) clusters of formula {Pd3[(NR)3PO](Cl)3}2 in octahedral and prismatic geometries. These clusters consist of two trinuclear Pd3‐motifs, each cis‐protected by a tris(alkylimido)phosphate trianion, which are linked together by six μ2‐Cl bridges. A staggered arrangement of the two imido‐Pd3 units results in the formation of octahedral clusters (R=iBu, nBu, cHex, iPr and nPr), while an eclipsed conformation (R=tBu) gives rise to a prismatic cluster. A similar prismatic configuration was obtained for the mixed‐bridged clusters {Pd3[(NR)3PO](OAc)2(Cl)}2 (R=cHex and iPr), formed in the reaction involving the corresponding phosphoric triamide, Pd(OAc)2 and Pd(PhCN)2Cl2. The reaction of an octahedral cluster {Pd3[(NnPr)3PO](Cl)3}2 with 1,1’‐ferrocene dicarboxylic acid (FDC−H) gave the prismatic cluster {Pd3[(NnPr)3PO](FDC)(Cl)}2 which again consists of a mixed‐bridged environment with FDC and Cl− linkers. Further, treatment of the octahedral {Pd3[(NnPr)3PO](Cl)3}2 cluster with iPrNH2, a stronger nucleophile, leads to its symmetric cleavage and forms the trinuclear cluster {Pd3[(NR)3PO]Cl3(R'NH2)3}. We have also shown the catalytic activity of some of these Pd(II) complexes in the Suzuki reactions in both organic and aqueous phase conditions which suggest that all these imido‐Pd(II) clusters are still suitable for catalytic reactions.

Continuous Load Scaling: New Method of Simulating Longitudinal Live Load Spreading for Two-Dimensional Analysis of Buried Culverts

Because of their prismatic configuration, buried culverts are often designed and analyzed as two-dimensional (2-D) plane strain soil structure systems, as exemplified by the Culvert Analysis and Design (CANDE) finite element program. One major difficulty with 2-D analysis is that live loads are not infinitely long prismatic strips but are finite footprints that induce load spreading through soil in the in-plane and out-of-plane directions. Because traditional 2-D analysis permits only in-plane load spreading, the predicted soil stresses are increasingly overestimated as soil depth increases. The traditional approach to correcting the overestimate is to reduce judiciously the 2-D strip load; this process is called the reduced surface load (RSL) procedure. The reduction factor is dependent on an assumed load-spreading theory and a selected soil depth ( H). RSL analysis results in soil stresses that are correct at the selected soil depth ( H) but understressed for depths less than H and overstressed for depths greater than H. The new continuous load scaling (CLS) procedure introduced in this paper overcomes such shortcomings by continually diverting live load in the longitudinal direction as a continuous function of soil depth. This diversion is achieved by continuously increasing the plane strain unit thickness as a function of depth on the basis of an assumed load-spreading theory. CANDE solutions were obtained for both RSL and CLS procedures and compared with three-dimensional solutions for free-field conditions and for flexible and rigid culvert installations. The bottom-line finding is that the CLS procedure with the elasticity-based load-spreading method is far superior to all other 2-D methods.

Imposing high-symmetry and tuneable geometry on lanthanide centres with chelating Pt and Pd metalloligands.

Exploitation of HSAB preferences allows for high-yield, one-pot syntheses of lanthanide complexes chelated by two Pd or Pt metalloligands, [MII(SAc)4]2- (SAc- = thioacetate, M = Pd, Pt). The resulting complexes with 8 oxygen donors surrounding the lanthanides can be isolated in crystallographically tetragonal environments as either [NEt4]+ (space group: P4/mcc) or [PPh4]+ (space group: P4/n) salts. In the case of M = Pt, the complete series of lanthanide complexes has been structurally characterized as the [NEt4]+ salts (except for Ln = Pm), while the [PPh4]+ salts have been structurally characterized for Ln = Gd-Er, Y. For M = Pd, selected lanthanide complexes have been structurally characterized as both salts. The only significant structural difference between salts of the two counter ions is the resulting twist angle connecting tetragonal prismatic and tetragonal anti-prismatic configurations, with the [PPh4]+ salts approaching ideal D4d symmetry very closely (φ = 44.52-44.61°) while the [NEt4]+ salts exhibit intermediate twist angles in the interval φ = 17.28-27.41°, the twist increasing as the complete 4f series is traversed. Static magnetic properties for the latter half of the lanthanide series are found to agree well in the high temperature limit with the expected Curie behavior. Perpendicular and parallel mode EPR spectroscopy on randomly oriented powder samples and single crystals of the Gd complexes with respectively Pd- and Pt-based metalloligands demonstrate the nature of the platinum metal to strongly affect the spectra. Consistent parametrization of all of the EPR spectra reveals the main difference to stem from a large difference in the magnitude of the leading axial term, B02, this being almost four times larger for the Pt-based complexes as compared to the Pd analogues, indicating a direct Pt(5d z2 )-Ln interaction and an arguable coordination number of 10 rather than 8. The parametrization of the EPR spectra also confirms that off-diagonal operators are associated with non-zero parameters for the [NEt4]+ salts, while only contributing minimally for the [PPh4]+ salts in which lanthanide coordination approximates D4d point group symmetry closely.

A Coarse-Mesh Coupled Neutronics and Thermal Fluids Method for Prismatic Cores

A newly developed coupled neutronic—thermal-hydraulic method for prismatic high-temperature gas reactors (HTGRs) is presented with accompanying results for several prismatic core configurations and numerical sensitivity studies. The principal advantage of the new method is the determination of coupled, whole-core temperature and pin power distributions with reduced computational effort over other available codes. The coarse-mesh radiation transport method (COMET), which relies solely on radiation transport, is the component of the new method used to compute neutronic parameters. A three-dimensional unit-cell—based thermal fluids solver is used to compute steady-state thermal-hydraulic parameters. For both component methods, no geometric approximations or averaging schemes are necessary. Convergence of the neutronic and thermal-hydraulic components and the coupled method is discussed, and coupled analyses are presented. The calculation of whole-core solutions allows for unique insights not possible with limited domain tools such as computational fluid dynamics. Results from one such unique study, near-critical control rod movements, are presented in this paper. Comparisons between coupled and uncoupled analyses are also presented.

A Techno-Economic Assessment of Cylindrical Spiral-Wound Lithium Ion Batteries: Can the Huge Factories Achieve Their Cost Goals?

This talk will examine the techno-economics of Li-ion battery production with a focus on assessing the potential economies of scale that are purported for very large factories. A full front-to-back manufacturing model has been developed to address this question. The model is based on the Argonne BatPac tool that was originally created to describe the production of prismatic pouch configuration cells and has been extended to describe spiral-wound 18650 cells. Three different cathode chemistries have been considered: NCA, LMO, or NMC, and the costs of producing cells and packs at different volumes with different supply chain inputs are assessed. Further, an analysis on the impact of the market price of lithium-containing precursors on battery and back costing will be offered. Our findings suggest that there is an absolute minimum in production cost for this format of these cells and this minimum is higher than values commonly described in the media. We also suggest that the price of lithium has little impact on cell and pack costing on a per kWh basis. We will offer a complete accounting of our analysis and an assessment of what materials and manufacturing changes stand to have the largest cost impact when producing cells and packs at a massive scale.

Effect of Crystal Orientation on Nanoindentation Behavior in Magnesium

The effect of crystal orientation on nanoindentation behavior at both quasi-static and high strain rates was investigated using single-crystalline magnesium oriented in basal and prismatic configurations. Both the basal and prismatic planes had similar activation volumes, 55 and 73b 3 for deformation at room temperature, as well as a small temperature dependence up to 423 K (150 °C). Microstructural observations beneath the indentations revealed that { $$ 10\bar{1}2 $$ } type deformation twins were formed in both orientations irrespective of testing temperature. With twins forming beneath the indenter and multiple orientations of loading, it is believed that cross-slip and/or multiple slip are likely rate-controlling for global deformation, which also aligns with observations on nanoindentation of polycrystalline coarse-grained magnesium. The locations of the twins were consistent with expectations based on indentation mechanics as assessed by finite element simulations. The finite element simulations also predicted that an indenter tip with a shaper tip radius would tend to promote { $$ 10\bar{1}2 $$ } twins.

Crystal structure of the salt bis-(tri-ethano-lamine-κ(4) N,O,O',O'')cadmium bis[2-(2-oxo-2,3-di-hydro-1,3-benzo-thia-zol-3-yl)acetate

The reaction of 2-(2-oxo-2,3-di-hydro-1,3-benzo-thia-zol-3-yl)acetic acid (NBTA) and tri-ethano-lamine (TEA) with Cd(CH3OO)2 resulted in the formation of the title salt, [Cd(C6H15NO3)2](C9H6NO3S)2. In its crystal structure, the complex cation [Cd(TEA)2](2+) and two independent NBTA(-) units with essentially similar geometries and conformations are present. In the complex cation, each TEA mol-ecule behaves as an N,O,O',O''-tetra-dentate ligand, giving rise to an eight-coordinate Cd(II) ion with a bicapped trigonal-prismatic configuration. All ethanol groups of each TEA mol-ecule form three five-membered chelate rings around the Cd(II) ion. The Cd-O and Cd-N distances are in the ranges 2.392 (2)-2.478 (2) and 2.465 (2)-2.475 (3) Å, respectively. O-H⋯O hydrogen bonds between the TEA hy-droxy groups and carboxyl-ate O atoms connect cationic and anionic moieties into chains parallel to [110]. Each NBTA(-) anion is additionally linked to a symmetry-related anion through π-π stacking inter-actions between the benzene and thia-zoline rings [minimum centroid-to-centroid separation = 3.604 (2) Å]. Together with additional C-H⋯O inter-actions, these establish a double-layer polymeric network parallel to (001).

Ferromagnetism in Transitional Metal-Doped MoS2 Monolayer.

Manipulating electronic and magnetic properties of two-dimensional (2D) transitional-metal dichalcogenides (TMDs) MX2 by doping has raised a lot of attention recently. By performing the first-principles calculations, we have investigated the structural, electronic, and magnetic properties of transitional metal (TM)-doped MoS2 at low and high impurity concentrations. Our calculation result indicates that the five elements of V-, Mn-, Fe-, Co-, and Cu-doped monolayer MoS2 at low impurity concentration all give rise to the good diluted magnetic semiconductors. By studying various configurations with different TM-TM separations, we found that the impurity atoms prefer to stay together in the nearest neighboring (NN) configuration, in which the doped TM atoms are FM coupling except for Fe doping at 12 % concentration. For V, Mn, and Fe doping, the total magnetic moment is smaller than the local magnetic moment of the dopants because the induced spins on the nearby host atoms are antiparallel to that of the doped atoms. In contrast, Co and Cu doping both give the higher total magnetic moment. Especially, Cu doping induces strong ferromagnetism relative to the local spins. However, the atomic structures of Co- and Cu-doped MoS2 deviate from the original prismatic configuration, and the magnetic moments of the doped systems decrease at 12 % impurity concentration although both elements give higher magnetic moments at 8 % impurity concentration. Our calculations indicate that V and Mn are promising candidates for engineering and manipulating the magnetism of the 2D TMDs.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1376-y) contains supplementary material, which is available to authorized users.

An aerodynamic and aeroelastic experimental study on a sectional and three-dimensional rectangular tall building

Summary This paper examines the aerodynamic properties of a rectangular tall building with sharp edges. The building has a section aspect ratio B/D = 2.6 and a height aspect ratio H/D = 9, giving in a quite slender prismatic configuration. The study was performed on sectional and three-dimensional models of the building. The sectional model was tested in a smooth flow condition, and the aerodynamic coefficients of the section were determined. Forces and pressure distributions were measured on the three-dimensional model to compare with the aerodynamic behavior of the sectional model. Both a rigid (non-moving) and a moving model of the building were tested to analyze possible aeroelastic effects. Different levels of incoming wind turbulence were tested, since this is a key parameter in the aerodynamic behavior of the rectangular prism. Copyright © 2015 John Wiley & Sons, Ltd.

The lanthanoid hydration properties beyond the ‘Gadolinium Break’: Dysprosium (III) and holmium (III), an ab initio quantum mechanical molecular dynamics study

A theoretical study of dysprosium(III) and holmium(III) in aqueous solution based on a quantum mechanical charge field-molecular dynamics (QMCF-MD) simulation is presented. The obtained structural and dynamical data were found to be in good agreement with several experimental and theoretical data. It is shown that the coordination number is constantly switching between eight and nine adopting square antiprismatic and tricapped trigonal prismatic configurations, thus supporting the interpretation of experimental data.

A Comparative Study of [CaEDTA](2-) and [MgEDTA](2-): Structural and Dynamical Insights from Quantum Mechanical Charge Field Molecular Dynamics.

Structure and dynamics of [MgEDTA](2-) and [CaEDTA](2-) complexes in aqueous solution have been investigated via quantum mechanical/molecular mechanical (QM/MM) simulations. While for the first a 6-fold octahedral complex has been observed, the presence of an additional coordinating water ligand has been observed in the latter case. Because of rapidly exchanging water molecules, this 7-fold coordination complex was found to form pentagonal bipyramidal as well as capped trigonal prismatic configurations along the simulation interchanging on the picosecond time scale. Also in the case of [MgEDTA](2-) a trigonal prismatic configuration has been observed for a very short time period of approximately 1 ps. This work reports for the first time the presence of trigonal prismatic structures observed in the coordination sphere of [MgEDTA](2-) and [CaEDTA](2-) complexes in aqueous solution. In addition to the detailed characterization of structure and dynamics of the systems, the prediction of the associated infrared spectra indicates that the ion-water vibrational mode found at approximately 250 cm(-1) provides a distinctive measure to experimentally detect the presence of the coordinating water molecule via low-frequency IR setups.

Indirect disturbance compensation control of a planar parallel (2-PRP and 1-PPR) robotic manipulator

Abstract This study addresses the dynamic modelling and indirect disturbance compensation control of planar parallel robotic motion platform with three degrees of freedom (3-DOF) in the presence of parameter uncertainties and external disturbances. The proposed planar parallel motion platform is a singularity free manipulator and has three manipulator legs located on the same plane linked with a moving platform. Of the three aforementioned manipulator legs, two legs have a prismatic–revolute–prismatic (PRP) joint configuration each with only one prismatic joint deliberated to be active, and the other leg consists of prismatic–revolute–prismatic (PPR) joint configuration with one active prismatic joint. The closed form kinematic solution (both forward and reverse kinematics) for the platform has been obtained in completion. In addition, the dynamic model for the platform has been communicated using the energy based Euler–Lagrangian formulation method. The proposed controller is based on a computer torque control with disturbance compensation integrated with it. Disturbance vectors comprising disturbances due to parameter variations, payload variations, frictional effects and other additional effects have been estimated using an extended Kalman filter (EKF). The EKF proposed for this specific platform uses only position and orientation measurements for estimation and noise mitigation. Simulations with a characteristic trajectory are presented and the results have been paralleled with traditional controllers such as the proportional integral derivative (PID) controller and computed torque controller (CTC). The results demonstrate satisfactory tracking performance for the proposed controller in the presence of parameter uncertainties and external disturbances.

Synthesis of Silver and Silver/Gold Anisotropic Nanostructures for Surface Enhanced Raman Spectroscopy Applications

We are reporting the one pot chemical reduction synthesis of isotropic spherical silver nanoparticles of size around 4-8 nm and some anisotropic nanostructures of silver and silver-gold systems such as silver nanoprisms of size around 60-80 nm, silver/gold prismatic core/shell nanostructures of size around 30-50 nm and alloy like silver-gold prismatic nanoframes of size around 40-60 nm and investigated their plasmonic properties for the surface enhanced Raman spectroscopy (SERS) applications. Morphology and shape dependent plasmonic properties of these nanostructures were characterized by using high resolution transmission electron microscopy (HRTEM) and UV-Visible spectroscopy techniques respectively. The surface enhanced Raman spectroscopy (SERS) properties of all the fabricated nanostructures were investigated on Methylene Blue (MB) molecule. A gradual improvement in the SERS effect was observed with respect to the change of morphology from spherical to nanoframes and the order of SERS effect was found to be nanoframes > core/shell prismatic nanostructures > nanoprisms > spherical nanoparticles. Our investigation revealed that the phenomenon of the improved SERS effect of anisotropic silver and silver-gold nanostructures is primarily attributed to their prismatic geometrical configurations.

Microtwinning as a common mechanism for the martensitic and pearlitic transformations

Abstract Common model for austenite transformations to pearlite and martensite has been proposed. The model uses a topological operation which is a local flipping of interatomic bonds resulting in formation of the structural unit of the coherent twin boundary. Main structural unit of a coherent twin boundary along {1 1 3} in the FCC lattice is a trigonal prism which is also the main building unit for the cementite structure. The atomic structure of such multiple {1 1 3} twins coincides with the structure of multiple twins along {1 1 2} of the BCC lattice, so the FCC–BCC transformation route is the FCC twinning along {1 1 3} and detwinning of {1 1 2} BCC twins into BCC structure. Carbon atoms serve as stabilizers to the prismatic iron configurations thus forming the cementite structure during pearlite transformation. High density of microtwins in the rest austenite after pearlite transformation in 1.2C–4Mn steel and new orientation relationships between pearlite constituents and austenite have been observed by transmission electron microscopy in full consistency with the proposed model. The twinning–detwinning mechanism prescribes also parallelism between {1 1 3} FCC and {1 1 2} BCC for martensite transformation in full accordance with published data.

A Coordination Chemistry Study of Solvated Thorium(IV) Ions in Two Oxygen‐Donor Solvents

AbstractThe structures of the dimethyl sulfoxide (dmso) and N,N′‐dimethylpropyleneurea (dmpu) solvated thorium(IV) ions have been studied in solution by extended X‐ray absorption fine structure (EXAFS), and the structure of the solid oxonium bis[nonakis(κO‐dimethyl sulfoxide)]thorium(IV) trifluoromethanesulfonate dihydrate, (H3O)[Th((CH3)2SO)9]2(CF3SO3)9·2H2O (1) has been determined by single‐crystal X‐ray diffraction and EXAFS. Compound 1 was crystallized by evaporating a saturated dmso solution. It consists of two individual nonakis(κO‐dimethyl sulfoxide)thorium(IV) units, both of which have a tricapped trigonal prismatic configuration, as also found in nonakis(dimethyl sulfoxide)thorium(IV) perchlorate previously reported. Mean Th–O bond lengths of 2.47 and 2.43 Å are found for the two structural units, respectively, for which the differences may be explained by differences in occupancy and temperature factors. The EXAFS data of 1 revealed mean Th–O and S–O bond lengths of 2.449(3) and 1.525(3) Å, respectively, and a Th–O–S bond angle of 135.2(5)° to give a Th···S distance of 3.665(7) Å. In dmso solution, the mean Th–O and S–O bond lengths are 2.447(3) and 1.534(3) Å, respectively, the Th–O–S bond angle is 133.5(5)°, and there is a Th···S distance of 3.672(7) Å. The Th–O bond‐length distribution is somewhat asymmetric in both samples with Rmax values of 2.424 and 2.422 Å for 1 and solution, respectively. In dmpu solution, the Th–O and C–O bond lengths are 2.404(5) and 1.264(2) Å, respectively, and there is a Th–O–C angle of 157.1(5)° to give a Th···C distance of 3.594(7) Å. The observed Th–O bond length indicates strongly that thorium(IV) is eight‐coordinate in dmpu.

ChemInform Abstract: Hydrated Metal Ions in Aqueous Solution: How Regular Are Their Structures?

AbstractReview: 106 refs.

Impact of PWR spent fuel variations on back-end features of advanced fuel cycles with tru-fueled VHTR

Alternative strategies are being considered as management option for current spent nuclear fuel transuranics (TRU) inventory. Creation of transmutation fuels containing TRU for use in thermal and fast reactors is one of the viable strategies. Utilization of these advanced fuels will result in transmutation and incineration of the TRU. The objective of this study is to analyze the impact of conventional PWR spent fuel variations on TRU-fueled very high temperature reactor (VHTR) systems. The current effort is focused on prismatic core configuration operated under a single batch once-through fuel cycle option. IAEA’s nuclear fuel cycle simulation system (VISTA) was used to determine potential PWR spent fuel compositions. Additional composition was determined from the analysis of United States legacy spent fuel that is given in the Yucca Mountain Safety Assessment Report. A detailed whole-core 3-D model of the prismatic VHTR was developed using SCALE5.1 code system. The fuel assembly block model was based on Japan’s HTTR fuel block configuration. To establish a reference reactor system, calculations for LEU-fueled VHTR were performed and the results were used as the basis for comparative studies of the TRU-fueled systems. The LEU fuel is uranium oxide at 15% 235U enrichment. The results showed that the single-batch core lifetimes ranged between 5 and 7 years for all TRU fuels (3 years in LEU), providing prolonged operation on a single batch fuel loading. Transmutation efficiencies ranged between 19% and 27% for TRU-based fuels (13% in LEU). Total TRU material contents for disposal ranged between 730 and 808 kg per metric ton of initial heavy metal loading, reducing TRU inventory mass by as much as 27%. Decay heat and source terms of the discharged fuel were also calculated as part of the spent fuel disposal consideration. The results indicated strong potential of TRU-based fuel in VHTR.

ChemInform Abstract: Kinetics of Intercalation of Lithium into NbSe3 and TiS2 Cathodes.

Titanium disulfide and niobium triselenide are two well-studied candidate materials for positive electrodes in rechargeable lithium cells. A comparative study of the kinetics of intercalation of lithium in both the cathodes is made here based on various electrochemical techniques, i.e., linear polarization, potentiodynamic polarization, and ac impedance under different experimental conditions such as prismatic or disk configuration of fresh, partially discharged, or cycled electrode. Further, the diffusion coefficients of lithium ions in these cathodes are estimated under these conditions using conventional techniques, i.e., ac impedance, chronocoulometry, chronoamperometry, and current pulse relaxation. Based on the values of the diffusion coefficients, the applicability of these methods for the determination of diffusion coefficients is discussed.

Hydrated metal ions in aqueous solution: How regular are their structures?

The hydration reaction is defined as the transfer of an ion or neutral chemical species from the gaseous phase into water, Mn+(g) → Mn+(aq). In this process, water molecules bind to metal ions through ion-dipole bonds of mainly electrostatic character. The hydration reaction is always strongly exothermic with increasing heat of hydration with increasing charge density of the ion. The structures of the hydrated metal ions in aqueous solution display a variety of configurations depending on the size and electronic properties of the metal ion. The basic configurations of hydrated metal ions in aqueous solution are tetrahedral, octahedral, square antiprismatic, and tricapped trigonal prismatic. This paper gives an overview of the structures of hydrated metal ions in aqueous solution with special emphasis on those with a non-regular coordination figure. Metal ions without d-electrons in the valance shell form regular aqua complexes with a coordination figure, allowing a maximum number of water molecules to be clustered around the metal ion. This number is dependent on the ratio of the metal ion radius to the atomic radius of oxygen in a coordinated water molecule (1.34 Å). The lighter lanthanoid(III) ions have a regular tricapped trigonal prismatic configuration with the M–O distance to the capping water molecules somewhat longer than to the prismatic ones. However, with increasing atomic number of the lanthanoid(III) ions, an increasing distortion of the capping water molecules is observed, resulting in a partial loss of water molecules in the capping positions for the heaviest lanthanoids. Metal ions with d4 and d9 valance shell electron configuration, as chromium(II) and copper(II), respectively, have Jahn–Teller distorted aqua complexes. Metal ions with low charge and ability to form strong covalent bonds, as silver(I), mercury(II), palladium(II), and platinum(II), often display distorted coordination figures due to the second-order Jahn–Teller effect. Metal ions with d10s2 valence shell electron configuration may have a stereochemically active lone electron pair (hemi-directed complexes) or an inactive one (holo-directed). The hydrated tin(II), lead(II), and thallium(I) ions are hemi-directed in aqueous solution, while the hydrated bismuth(III) ion is holo-directed. The structures of the hydrated cationic oxo-metal ions are reported as well.